Noninvasive continuous blood pressure measuring apparatus and a method of noninvasively measuring continuous blood pressure

ABSTRACT

One of pairs of an exciter and a sensor is selected in accordance with the detection signal which is derived from an exciter waveform induced in an artery transmitted therethrough. The pairs of exciters and sensors are arranged on a substrate in various formations. A/D converters are provided to respective detection signals. A frequency of the oscillation signal supplied to the exciter is controlled by various oscillation signal generation circuits. Bandpass filtering for extracting the exciter waveform, low-pass-filtering for extracting a natural blood pressure waveform, phase difference detection processes are provided by a microprocessor, wherein the bandpass filtering and low-pass-filtering processes may be replaced with a bandpass filter and a low pass filter, and their outputs are selected by a switching circuit and supplied to the microprocessor through one a/d converter. The frequency of the oscillation signal is controlled to an optimum frequency by detecting the detection signal and estimating the attenuation, dispersion, phase shift with respect to different frequency and by determining one of the different frequency in accordance with the estimation result. The waveform of the oscillation signal is controlled to an optimum waveform similarly.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a noninvasive continuous blood pressuremeasuring apparatus for noninvasively, continuously measuring bloodpressure and a method of noninvasively measuring continuous bloodpressure.

2. Description of the Prior Art

A noninvasive continuous blood pressure measuring apparatus fornoninvasively, continuously measuring blood pressure is known. Anapparatus and a method for measuring an induced perturbation todetermine a blood pressure is disclosed in U.S. Pat. No. 5,590,649. Inthis prior art apparatus, a monitor for continuously determining apatient's physiological parameter includes a means for obtaining aperiodic calibration measurement of the patient's physiologicalparameter. An exciter, positioned over an artery of the patient inducesan exciter waveform into the patient's arterial blood. A noninvasivesensor, positioned over the artery, senses a hemoparameter and providesa noninvasive sensor signal output representative of the hemoparameter.A processor receives the calibration measurement and noninvasive sensorsignal output. The processor determines a SC offset based on thecalibration measurement and processes the noninvasive sensor signal tocontinuously determine the patient's physiological parameter.

SUMMARY OF THE INVENTION

The aim of the present invention is to provide a superior noninvasivecontinuous blood pressure measuring apparatus and a superior method ofnoninvasively measuring continuous blood pressure.

According to this invention, there is provided a first noninvasivecontinuous blood pressure measuring apparatus including: an oscillatorfor generating an oscillation signal having a desired frequency and adesired amplitude; a substrate; a plurality of exciters arranged on thesubstrate in a direction responsive to the oscillation signal forinducing exciter waveforms in an artery and a blood in the artery of aliving body; a plurality of sensors respectively arranged on thesubstrate in the direction a predetermined interval apart from theexciters for receiving induced exciter waveforms transmitted through theartery from the living body and outputting detection signals; amultiplexer for effecting recurrently switching and time-divisionallyoutputting outputs of the sensors; a determining and selecting portionresponsive to the multiplexer for determining one of the outputs inaccordance with a predetermined judging condition and for selecting andoutputting one of the outputs; a calibration hemadynamometer fordetecting absolute values of a maximum blood pressure and a minimumblood pressure of the living body; a calculating portion for receivingthe absolute values from the hemadynamometer and successivelycalculating and outputting an instantaneous blood pressure value from aphase relation between the oscillation signal and one of the outputsfrom the determining and selecting portion and the absolute values; anda display for displaying a continuous blood pressure variation from theinstantaneous blood pressure successively outputted by the calculationportion.

In the first noninvasive continuous blood pressure measuring apparatus,the substrate correspondingly arranges the exciters and the sensors suchthat each pair of each of the exciters and each of the sensors isarranged in the direction and the exciter and the sensor of each pairare arranged in a second direction perpendicular to the direction, theapparatus further including an attaching unit for attaching thesubstrate to the living body.

In the first noninvasive continuous blood pressure measuring apparatus,the substrate may correspondingly arranges the exciter and the sensorssuch that each pair including two of the sensors and one of the exciterarranged between the two of the sensors with the predetermined distanceis arranged in the direction, the apparatus may further include anattaching unit for attaching the substrate to the living body.

The first noninvasive continuous blood pressure measuring apparatus mayfurther include: a plurality of a/d converters for respectivelya/d-converting the detection signals and supplying converted signals tothe determining and selecting portion as the outputs of the sensors.

According to this invention, there is a second noninvasive continuousblood pressure measuring apparatus is provided which includes: anoscillator for generating an oscillation signal having a desiredfrequency and a desired amplitude; an exciter arranged responsive to theoscillation signal for inducing an exciter waveform in an artery and ablood in the artery of a living body; a sensor arranged a predeterminedinterval apart from the exciter for receiving the induced exciterwaveform transmitted through the artery from the living body andoutputting detection signal; a calibration hemadynamometer for detectingabsolute values of a maximum blood pressure and a minimum blood pressureof the living body; a calculating portion for receiving absolute valuesfrom the calibration hemadynamometer and successively calculating andoutputting an instantaneous blood pressure value from a phase relationbetween the oscillation signal and the detection signal and the absolutevalues; and a display for displaying a continuous blood pressurevariation from the instantaneous blood pressure successively outputtedby the calculation portion.

In the second noninvasive continuous blood pressure measuring apparatus,the oscillator may include: a clock signal generation circuit forgenerating a clock signal; a processor responsive to frequency controldata and the clock signal for successively generating frequency signaldata indicative of amplitude in time base in accordance with thefrequency control data; a d/a converter for converting the frequencysignal data; and a filter for low-pass filtering an output of the d/aconverter and outputting the oscillation signal of which frequency iscontrolled in accordance with the frequency data.

In the second noninvasive continuous blood pressure measuring apparatus,the oscillator may include: a clock signal generation circuit forgenerating a clock signal; a numerically-controlled oscillatorresponsive to frequency control data and the clock signal forsuccessively generating frequency signal data indicative of amplitude intime base in accordance with the frequency control data; a d/a converterfor converting the frequency signal data; and a filter for low-passfiltering an output of the d/a converter and outputting the oscillationsignal of which frequency is controlled in accordance with the frequencydata.

In the second noninvasive continuous blood pressure measuring apparatus,the oscillator may include: a clock signal generation circuit forgenerating a clock signal; a processor responsive to frequency controldata for generating at least one cycle of frequency signal data andstoring one cycle of frequency signal data in a look-up table; anaddress signal generating circuit for generating an address signal inresponse to the clock signal to operate the look-up table tosuccessively read and output one cycle of frequency data indicative ofan amplitude of the oscillation signal; a d/a converter for convertingone cycle of frequency data; and a filter for low-pass filtering anoutput of the a/d converter and outputting the oscillation signal ofwhich frequency is controlled in accordance with the frequency data.

In the second noninvasive continuous blood pressure measuring apparatus,the oscillator may include: a PLL circuit responsive to frequencycontrol data for successively generating a frequency signal; and afilter for low-pass filtering the frequency signal and outputting thefiltered frequency signal as the oscillation signal of which frequencyis controlled in accordance with the frequency data.

According to this invention, there is provided a third noninvasivecontinuous blood pressure measuring apparatus which includes: anoscillator for generating an oscillation signal having a desiredfrequency and a desired amplitude; an exciter responsive to theoscillation signal for inducing an exciter waveform in an artery and ablood in the artery of a living body; a sensor arranged a predeterminedinterval apart from the exciter for receiving the induced exciterwaveform transmitted through the artery from the living body andoutputting detection signal; an a/d converter for a/d-converting thedetection signal; a calibration hemadynamometer for detecting absolutevalues of a maximum blood pressure and a minimum blood pressure of theliving body; a microprocessor including a filter portion and acalculating portion, the filter portion band-pass-filtering thedetection signal from the a/d converter, the calculating portionreceiving the absolute values from the calibration hemadynamometer andsuccessively calculating and outputting an instantaneous blood pressurevalue from a phase relation between the oscillation signal and thedetection signal from the filter portion and the absolute values; and adisplay for displaying a continuous blood pressure variation from theinstantaneous blood pressure successively outputted by the calculationportion.

According to this invention, there is provided a fourth noninvasivecontinuous blood pressure measuring apparatus which includes: anoscillator for generating an oscillation signal having a desiredfrequency and a desired amplitude; an exciter responsive to theoscillation signal for inducing an exciter waveform in an artery and ablood in the artery of a living body; a sensor arranged a predeterminedinterval apart from the exciter for receiving the induced exciterwaveform transmitted through the artery from the living body andoutputting detection signal; a calibration hemadynamometer for detectingabsolute values of a maximum blood pressure and a minimum blood pressureof the living body; a bandpass filter for band-pass-filtering thedetection signal from the sensor; an a/d converter for a/d-convertingthe detection signal from the bandpass filter; a microprocessorincluding a calculating portion for receiving the absolute values fromthe calibration hemadynamometer and successively calculating andoutputting an instantaneous blood pressure value from a phase relationbetween the oscillation signal and the detection signal from the a/dconverter and the absolute values; and a display for displaying acontinuous blood pressure variation from the instantaneous bloodpressure successively outputted by the calculation portion.

According to this invention, there is provided a fifth noninvasivecontinuous blood pressure measuring apparatus which includes: anoscillator for generating an oscillation signal of which frequency iscontrolled; an exciter responsive to the oscillation signal for inducingan exciter waveform in an artery and a blood in the artery of a livingbody; a sensor arranged a predetermined interval apart from the exciterfor receiving the induced exciter waveform transmitted through theartery from the living body and outputting detection signal; acalibration hemadynamometer for detecting absolute values of a maximumblood pressure and a minimum blood pressure of the living body; afrequency determining portion responsive to the sensor for controllingthe oscillator to successively control the frequency at differentfrequencies and determining one of the difference frequencies inaccordance with the detection signal outputted at different frequencies,and then, controlling the oscillator to continuously generate theoscillation signal at one of the different frequencies; a calculatingportion responsive to the frequency determining portion for receivingabsolute values from the calibration hemadynamometer and successivelycalculating and outputting an instantaneous blood pressure value from aphase relation between the oscillation signal and the detection signalat one of the different frequencies and the absolute values; and adisplay for displaying a continuous blood pressure variation from theinstantaneous blood pressure successively outputted by the calculationportion.

In the fifth noninvasive continuous blood pressure measuring apparatus,the frequency determining portion may detect attenuations in thedetection signal at different frequencies and determine one of thedifference frequencies in accordance with a minimum of the attenuations.

In the fifth noninvasive continuous blood pressure measuring apparatus,the frequency determining portion may detect dispersions in amplitudesof the detection signal at different frequencies and determine one ofthe different frequencies in accordance with a minimum of thedispersions.

In the fifth noninvasive continuous blood pressure measuring apparatus,the frequency determining portion may detect phase shifts in thedetection signal at different frequencies and determine one of thedifference frequencies in accordance with a maximum of the phase shifts.

In the fifth noninvasive continuous blood pressure measuring apparatus,the frequency determining portion may detect attenuations in thedetection signal at different frequencies, detect dispersions inamplitudes of the detection signal at the different frequencies, anddetect phase shifts in the detection signal at the differentfrequencies, obtain estimation values at the different frequenciesthrough an estimating function for estimating the attenuations, thedispersions, and the phase shifts, and determine one of the differencefrequencies in accordance with the estimation values at the differentfrequencies.

According to this invention, there is provided a sixth noninvasivecontinuous blood pressure measuring apparatus which includes: anoscillator for generating an oscillation signal of which waveform iscontrolled; an exciter responsive to the oscillation signal for inducingan exciter waveform in an artery and a blood in the artery of a livingbody; a sensor arranged a predetermined interval apart from the exciterfor receiving the induced exciter waveform transmitted through theartery from the living body and outputting detection signal; acalibration hemadynamometer for detecting absolute values of a maximumblood pressure and a minimum blood pressure of the living body; awaveform determining portion responsive to the sensor for controllingthe oscillator to control the oscillation signal successively havedifferent waveforms and determining one of the difference waveforms inaccordance with the detection signal outputted at different waveformsand then, controlling the oscillator to continuously generate theoscillation signal at one of the different waveforms; a calculatingportion responsive to the frequency determining portion for receivingabsolute values from the calibration hemadynamometer and successivelycalculating and outputting an instantaneous blood pressure value from aphase relation between the oscillation signal and the detection signalat one of the different waveforms and the absolute values; and adisplaying for displaying a continuous blood pressure variation from theinstantaneous blood pressure successively outputted by the calculationportion.

In the sixth noninvasive continuous blood pressure measuring apparatus,the waveform determining portion may detect attenuations in thedetection signal at the different waveforms and determine one of thedifference waveforms in accordance with a minimum of the attenuations.

In the sixth noninvasive continuous blood pressure measuring apparatus,the waveform determining portion may detect dispersions in amplitudes ofthe detection signal at the different waveforms and determines one ofthe difference waveforms in accordance with a minimum of thedispersions.

In the sixth noninvasive continuous blood pressure measuring apparatus,the waveform determining portion may detect phase shifts in thedetection signal at the different waveforms and determine one of thedifference waveforms in accordance with a maximum of the phase shifts.

In the sixth noninvasive continuous blood pressure measuring apparatus,the waveform determining portion may detect attenuations in thedetection signal at the different waveforms, detect dispersions inamplitudes of the detection signal at the different waveforms, anddetect phase shifts in the detection signal at the different waveforms,obtain estimation values at the different waveforms through anestimating function for estimating the attenuations, the dispersions,and the phase shifts, and determine one of the difference waveforms inaccordance with the estimation values at the different waveforms.

According to this invention, there is provided a first method ofnoninvasively measuring continuous blood pressure including the stepsof: generating an oscillation signal of which frequency is controlled;providing an exciter responsive to the oscillation signal inducing anexciter waveform in an artery and a blood in the artery of a livingbody; providing a sensor arranged a predetermined interval apart fromthe exciter for receiving the induced exciter waveform transmittedthrough the artery from the living body and outputting detection signal;detecting absolute values of a maximum blood pressure and a minimumblood pressure of the living body; controlling the oscillation signal tosuccessively control the frequency at different frequencies anddetermining one of the difference frequencies in accordance with thedetection signal outputted at different frequencies; continuouslygenerating the oscillation signal at one of the different frequencies;receiving absolute values and successively calculating and outputting aninstantaneous blood pressure value from a phase relation between theoscillation signal and the detection signal at one of the differentfrequencies and the absolute values; and displaying a continuous bloodpressure variation from the instantaneous blood pressure successivelyoutputted.

According to this invention, there is provided a second method ofnoninvasively measuring continuous blood pressure including the stepsof: generating an oscillation signal of which waveform is controlled;providing an exciter responsive to the oscillation signal inducing anexciter waveform in an artery and a blood in the artery of a livingbody; providing a sensor arranged a predetermined interval apart fromthe exciter for receiving the induced exciter waveform transmittedthrough the artery from the living body and outputting detection signal;detecting absolute values of a maximum blood pressure and a minimumblood pressure of the living body; controlling the oscillation signal tosuccessively control the frequency at different waveforms anddetermining one of the difference waveforms in accordance with thedetection signal outputted at different waveforms; continuouslygenerating the oscillation signal at one of the different waveforms;receiving absolute values and successively calculating and outputting aninstantaneous blood pressure value from a phase relation between theoscillation signal and the detection signal at one of the differentwaveforms and the absolute values; and displaying a continuous bloodpressure variation from the instantaneous blood pressure successivelyoutputted.

BRIEF DESCRIPTION OF THE DRAWINGS

The object and features of the present invention will become morereadily apparent from the following detailed description taken inconjunction with the accompanying drawings in which:

FIG. 1 is a block diagram of a noninvasive continuous blood pressuremeasuring apparatus of a first embodiment of this invention;

FIG. 2 is a plan view of a sensor unit of the first embodiment;

FIG. 3 is a cross-sectional side view of the sensor unit of the firstembodiment taken on line III—III;

FIGS. 4A to 4E are graphical drawings of the first embodiment showingthe determining operation;

FIG. 5A is a plan view of a sensor unit of a second embodiment;

FIG. 5B is a cross-sectional side view of the sensor unit of the secondembodiment taken on the line VB in FIG. 5A;

FIG. 6 is a block diagram of a noninvasive continuous blood pressuremeasuring apparatus of a third embodiment of this invention;

FIG. 7 is a block diagram of a noninvasive continuous blood pressuremeasuring apparatus of a fourth embodiment of this invention;

FIG. 8 is a block diagram of the fourth embodiment, wherein theoperation of the microprocessor is equivalently shown;

FIG. 9 is a block diagram of a noninvasive continuous blood pressuremeasuring apparatus of a fifth embodiment of this invention;

FIG. 10 is a block diagram of a noninvasive continuous blood pressuremeasuring apparatus of a sixth embodiment of this invention;

FIG. 11 is a block diagram of a noninvasive continuous blood pressuremeasuring apparatus of a seventh embodiment of this invention;

FIG. 12 is a block diagram of a noninvasive continuous blood pressuremeasuring apparatus of an eighth embodiment of this invention;

FIGS. 13A and 13B are graphical drawing of the eighth embodiment;

FIG. 14 is a block diagram of a noninvasive continuous blood pressuremeasuring apparatus of a ninth embodiment of this invention;

FIG. 15 is a block diagram of a noninvasive continuous blood pressuremeasuring apparatus of a tenth embodiment of this invention;

FIG. 16 depicts a flow chart of the tenth embodiment showing anoperation of the microprocessor;

FIG. 17 depicts a flow chart of the tenth embodiment showing anoperation of the frequency determining portion;

FIG. 18 is a graphical drawing of the tenth embodiment;

FIG. 19 is a block diagram of a noninvasive continuous blood pressuremeasuring apparatus of an eleventh embodiment of this invention;

FIG. 20 depicts a flow chart of the eleventh embodiment showing anoperation of the microprocessor; and

FIG. 21 depicts a flow chart of the eleventh embodiment showing anoperation of the waveform determining portion.

The same or corresponding elements or parts are designated with likereferences throughout the drawings.

DETAILED DESCRIPTION OF THE INVENTION

(First Embodiment)

FIG. 1 is a block diagram of a noninvasive continuous blood pressuremeasuring apparatus of a first embodiment of this invention. FIG. 2 is aplan view of a sensor unit of the first embodiment. FIG. 3 is a sidecross-sectional view of the sensor unit of the first embodiment taken online III—III.

The noninvasive continuous blood pressure measuring apparatus of thefirst embodiment includes an oscillator 1 for generating an oscillationsignal 31 having a predetermined (desired) frequency and a predeterminedamplitude, a plurality of exciters 2 (2 a to 2 d) arranged in adirection X with a distance D1, responsive to the oscillation signal 31,for inducing exciter waveforms in an artery 20 and a blood 23 in theartery 20 of a living body (arm) 21, a plurality of sensors 3 (3 a to 3h) arranged in the direction X with a distance D1 and apart from thecolumn of the exciters 2 by a distance D2 respectively for receivingexciter waveforms from the living body 21 and outputting detectionsignals 100 a to 100 g, respectively, a timing signal generating circuit9 for generating timing signals 9 a and 9 b, a multiplexer 4 forswitching and recurrently outputting one of outputs of the sensors 3 ato 3 h in response to the timing signal 9 a, a/d converter 5 fora/d-converting one of the outputs of the sensors 3 from the multiplexer4, a determining portion 10 responsive to the multiplexer 4 through thea/d converter 5 for determining one of the outputs in accordance with anoutput of the multiplexer 4 and a predetermined judging condition suchas amplitude, a calibration hemadynamometer 6 for detecting absolutevalues of a maximum blood pressure and a minimum blood pressure of theliving body, a calculating portion 7 for operating the calibrationhemadynamometer 6 and successively calculating and outputting aninstantaneous blood pressure value from a phase relation between theoscillation signal 31 and one of the outputs 100 a to 100 g indicated bythe determination result from the determining portion 10 and theabsolute values, and a display 8 for displaying a continuous bloodpressure variation from the instantaneous blood pressure successivelyoutputted by the calculation portion 7. The calibration hemadynamometer6 may measure the absolute values of a maximum blood pressure and aminimum blood pressure of the living body periodically withoutcontrolling by the calculation portion 7. The distance D2 is constant.On the other hand, the display D1 can be varied with every sensor 3 tosurely detect the exciter waveforms.

The sensor unit 19 includes a substrate 22, the exciters 2 a to 2 d, andsensors 3 a to 3 h, and an attaching belt 18 as shown in FIG. 2. Theexciters 2 and the sensors 3 includes flexible plates (not shown) andpiezoelectric element (not shown) sandwiched between the flexibleplates, so called bimorph. The exciter 2 generates vibrations withbending in the plates generated by the piezoelectric elements.Inversely, the sensor 3 generates the detection signal from thepiezoelectric element therein in accordance with the vibrations from theliving body 21.

The oscillator 1 generating the oscillation signal 31 having the desiredfrequency and the predetermined amplitude to induce exciter a favourablewaveform in the blood 23 in the artery 20. The exciters 2 a to 2 drespectively induce exciter waveforms in the artery 20 and the blood 23in the artery 20 of a living body (arm) 21 in response to theoscillation signal 31. The exciter waveforms (vibrations) induced in theblood 23 transmit through the blood in the artery 20 and reach thesensors 3 a to 3 d. The sensors 3 a to 3 h receive exciter waveformsfrom the living body 21, i.e., the induced exciter waveformstransmitting through the artery 20 and output detection signals 100 a to100 g. The timing signal generating circuit 9 generates timing signals 9a and 9 b. The multiplexer 4 recurrently selecting and outputting one ofdetection signals 100 a to 100 g of the sensors 3 a to 3 h in responseto the timing signal 9 a. The a/d converter 5 a/d-converts one of thedetection signals 100 a to 100 g of the sensor 3 a to 3 h. Thedetermining portion 10 determines one of the a/d-converted detectionsignals in accordance with a/d-converted detection signals and apredetermined judging condition such as amplitude of the detectionsignals.

The calibration hemadynamometer 6 detects absolute values of a maximumblood pressure and a minimum blood pressure of the living body 21periodically or detects the absolute values in response to a command 7 afrom the calculation portion 7. The calculating portion 7 operates thecalibration hemadynamometer 6 and successively calculates and outputsthe instantaneous blood pressure value from a phase relation between theoscillation signal 31 and one of the outputs 100 a to 100 g indicated bythe determining result from the determining portion 10 and the absolutevalues. The display 8 displays the continuous blood pressure variationfrom the instantaneous blood pressure successively outputted by thecalculation portion 7.

The determining operation will be described more specifically.

FIGS. 4A to 4E are graphical drawings of the first embodiment showingthe determining operation. For convenience of explanation, it is assumedthat one of the detection signals is determined between two detectionsignals 100 c and 100 d which are near the artery 20.

The sensors 100 c and 100 d outputs the detection signals as shown inFIGS. 4A and 4B, wherein an amplitude of the detection signal 100 c ishigher than that of the detection signal 100 d because the exciter 2 cand the sensor 3 c are just above the artery 20 as shown in FIG. 2.

The multiplexer 4 multiplexes the detection signals 100 c and 100 d inresponse to the timing signal 9 a as shown in FIG. 4C.

The a/d converter 4 a/d-converts the outputs of the multiplexer 4 asshown in FIG. 4D. The determining portion 10 compares the amplitude AMcof the a/d converted detection signal from the sensor 3 c with theamplitude AMd of the a/d-converted detection signal 3 d with referenceto the timing signal 9 a and determines the a/d-converted detectionsignal from the sensor 3 c because the amplitude AMc is higher than theamplitude AMd from the sensor 3 d. Then, the determining portion 10selects and outputs a determined detection signal from the sensor 3 c.In this embodiment, determining one of the a/d converted detectionsignal has been described with assumption that the detection signal isinduced from the exciter waveform through the artery 20. However, it isalso possible to determine one of the a/d-converted detection signalfrom the amplitude induced by the pulsation of the artery 20, that is,natural blood pressure waves. In this case, a frequency of the naturalblood pressure waves is lower than the frequency of the oscillationsignal 31, so that this signal is better in consideration of switchingtiming of the multiplexer 4 and the analog-to-digital converting rate.

In this case, a sampling frequency in the a/d converter 5 per onedetection signal is equal to or more than 200 Hz. Accordingly, theresultant sampling frequency of the a/d converter 5 is equal to or morethan 1600 Hz because there are eight sensor 3 a to 3 h.

The calculation portion 7 calculates and outputs the instantaneous bloodpressure value from a phase relation between the oscillation signal 31and one of the detection signals 100 a to 100 g indicated by thedetermining result from the determining portion 10 and the absolutevalues. That is, the method of calculating the blood pressure from thesound velocity through artery is known and described in U.S. Pat. No.5,590,649, the disclosure of which is hereby incorporated by reference.

In FIG. 2, the substrate 22 correspondingly arranges the exciter units 2a to 2 d and the sensors 3 a to 3 h such that each pair (for example, 2a, 3 a, and 3 e) includes two of the sensors 3 and one of the exciters 2arranged between two of the sensors with the distance D2 and is arrangedin the direction X, so that it is easy to attach the substrate 22 withthe attaching belt 18 because accurate positioning with respect to theartery 20 can be omitted by the selecting operation of the detectionsignals. In FIG. 2, the detection signal 100 g may be selected bydetermining portion 10 in accordance with the amplitudes of thedetection signals 100 c and 100 g. Moreover, it is possible to selectthe sensor 3 positioned upstream of the artery 20 or positioneddownstream with respect to the exciter 2 at will with a requestreceiving portion (not shown).

(Second Embodiment)

FIG. 5A is a plan view of a sensor unit of a second embodiment. FIG. 5Bis a cross-sectional side view of the sensor unit of the secondembodiment taken on the line VB in FIG. 5A.

The sensor unit of the second embodiment includes a substrate 22,exciters 2 a to 2 h, sensors 3 a to 3 h, and an attaching belt 18. Acolumn 2 q of the exciters 2 e to 2 h and corresponding column 3 q ofthe sensors 3 e to 3 h are shifted in the direction X from the column 2p of the exciters 2 a to 2 d and the column 3 p of the sensors 3 a to 3d by a distance D3 which is a half of the distance (pitch) D1. Theexciters 2 a to 2 d and the sensors 3 a to 3 d are arranged with thedistance D1 in direction X which substantially corresponds to the sizeof the exciters 2 a to 2 d and the sensors 3 a to 3 d in the directionX. Therefore, the exciters 2 a to 2 d and the sensors 3 a to 3 d arearranged compactly and selecting one of the detection signals areprecisely effected.

(Third Embodiment)

FIG. 6 is a block diagram of a noninvasive continuous blood pressuremeasuring apparatus of a third embodiment of this invention. Thenoninvasive continuous blood pressure measuring apparatus of the thirdembodiment is substantially the same as that of the first embodiment.The difference is that a/d converters 11 a to 11 h are respectivelyprovided to the detection signals 100 a to 100 h instead the multiplexer4 and the a/d converter 5. The a/d converters 11 a to 11 h a/d-convertsthe detection signals 100 a to 100 h independently. The determiningportion 10 selects and outputs a determined detection signal from thesensor 3.

The calculating portion 7 operates the calibration hemadynamometer 6 andsuccessively calculates and outputs the instantaneous blood pressurevalue from a phase relation between the oscillation signal and one ofthe outputs 100 a to 100 g from the determining portion 10 and theabsolute values. The display 8 displays the continuous blood pressurevariation from the instantaneous blood pressure successively outputtedby the calculation portion 7.

In the third embodiment, a total sampling rate of the a/d converters 11a to 11 h is increased, so that an accuracy in measuring the continuousblood pressure variation is improved.

(Fourth Embodiment)

FIG. 7 is a block diagram of a noninvasive continuous blood pressuremeasuring apparatus of a fourth embodiment of this invention. Thenoninvasive continuous blood pressure measuring apparatus of the fourthembodiment is substantially the same as that of the first embodiment.The difference is that a frequency of the oscillator 1 a is controlled.

The oscillator 1 a includes a clock signal generation circuit 212 forgenerating a clock signal; a microprocessor 210, including a memory 211,responsive to frequency control data and the clock signal forsuccessively generating frequency signal data 210 a indicative ofamplitude in time base in accordance with the frequency control data; ad/a converter 213 for converting the frequency signal data, andoutputting a frequency signal; and a filter 214 for low-pass-filteringthe frequency signal and outputting the filtered frequency signal as theoscillation signal of which frequency controlled in accordance with thefrequency data.

FIG. 8 is a block diagram of the fourth embodiment, wherein theoperation of the microprocessor 210 is equivalently shown.

The clock signal generation circuit 212 generates the clock signal 215and a conversion timing signal for the a/d converter 213. Themicroprocessor 210 starts an operation for calculating frequency signaldata 210 a indicative of amplitude in response to every clock signal 215from the clock signal generation circuit 212 using the memory 211 as awork memory by the known double integration method. The a/d converter213 converts the frequency signal data to generate the oscillationsignal. The filter 214 filters the oscillation signal from the a/dconverter 213 to remove unnecessary frequency components to supply theoscillation signal 214 a with low spurious.

The calculation portion 7 may be provided by the same microprocessor210.

FIG. 8 shows a circuit which is equivalent to the operation of themicroprocessor 210.

The circuit for effecting the double integration method includes firstintegrator 250, an inverter for inverting an output of the integrator250, and a second integrator 252 for integrating an output of theinverter 251 and outputting sine data 254 and feed back data which issupplied to the first integrator 250.

The first integrator 250 includes an adder 253, a multiplier 257, adelay 256. The adder 253 sums the feedback data from a multiplier 260 inthe second integrator 252, an output of the delay 256 and a triggersignal 261 which is generated once at start of the operation of theoscillator 1 a. The summing result is supplied to the delay 256 and tothe multiplier 257 and outputted as a cosine data 255. The multiplier257 multiplies the cosine data 255 with frequency data “a”. The delay256 supplied with the clock signal 215 delays the summing result of theadder 253 by one clock period of the clock signal 215.

The inverter 251 having a gain of −1 and inverts the multiplying result.

The second integrator 252 includes an adder 258, a multiplier 260, and adelay 259. The adder 258 sums an output of the delay 259 and an outputof the inverter 251 The summing result of the adder 258 is supplied tothe delay 259 and outputted as a sine data 254. The delay 259 suppliedwith the clock signal 215 delays the summing result of the adder 258 byone clock period of the clock signal 215. The output of the delay 259 issupplied to the multiplier 260 which multiplies the output of the delay259 with the frequency data “a” and supplies the feedback data to theadder 253 as mentioned. The delay 256 and 259 are supplied with theclock signal 215 to delay the cos data 255 and the sin data 254 by oneclock signal interval.

This circuit generates the oscillation signal 214 a of which frequency fis given by:

f=(a×T)/(2×π)

where T is a frequency of the clock signal 215 generated by the clocksignal generation circuit 212.

As mentioned, the circuit generates the oscillation signal 214 a ofwhich frequency f is controlled by the frequency control data “a”.Moreover, as the oscillation signal, the sine data 254 and the cosinedata 255 are generated and are also supplied to the calculation portion7 at the same time.

(Fifth Embodiment)

FIG. 9 is a block diagram of a noninvasive continuous blood pressuremeasuring apparatus of a fifth embodiment of this invention. Thenoninvasive continuous blood pressure measuring apparatus of the fifthembodiment is substantially the same as that of the fourth embodiment.The difference is in the structure of the oscillator 1 b. The oscillator1 b includes a clock signal generation circuit 222 for generating aclock signal; a microprocessor 220 for receiving frequency control data;a numerically-controlled oscillator 221 for successively generatingfrequency control data indicative of amplitude in time base inaccordance with the frequency control data; a d/a converter 223 forconverting the frequency signal data, and outputting a frequency signal;and a filter 224 for low-pass-filtering the frequency signal andoutputting the filtered frequency signal as the oscillation signal ofwhich frequency controlled in accordance with the frequency data “a”.

The microprocessor 220 receives the frequency control data. Thenumerically-controlled oscillator 221 successively generates thefrequency control data in accordance with the frequency control data.The d/a converter 223 converts the frequency signal data and outputs afrequency signal. The filter 224 low-pass-filters the frequency signaland outputting the filtered frequency signal as the oscillation signalof which frequency controlled in accordance with the frequency data “a”.

(Sixth Embodiment)

FIG. 10 is a block diagram of a noninvasive continuous blood pressuremeasuring apparatus of a sixth embodiment of this invention. Thenoninvasive continuous blood pressure measuring apparatus of the sixthembodiment is substantially the same as that of the fourth embodiment.The difference is in the structure of the oscillator 1 c. The oscillator1 c includes a clock signal generation circuit 232 for generating aclock signal; a look-up table 231; a microprocessor 230 for receivingfrequency control data and generating a set of frequency signal dataindicative of amplitude for one cycle of the oscillation signal inaccordance with the frequency control data and storing the frequencysignal data in a look-up table 231; an address signal generation circuit233 for successively generating an address signal in response to theclock signal to operate the look-up table 231 to successively outputinstantaneous frequency signal data; a d/a converter 234 fora/d-converting the frequency signal data and outputting a frequencysignal; and a filter 235 for low-pass-filtering the frequency signal andoutputting the filtered frequency signal as the oscillation signal ofwhich frequency controlled in accordance with the frequency data “a”.

The microprocessor 220 receives the frequency control data and generatesthe set of frequency signal data indicative of amplitude for one cycleof the oscillation signal in accordance with the frequency control dataand stores the frequency signal data in the look-up table 231 before thestart of measuring the blood pressure. The address signal generationcircuit 233 successively generates the address signal in response to theclock signal to operate the look-up table 231 to successively output theinstantaneous frequency signal data. The d/a converter 234 d/d-convertsthe frequency signal data and outputs the frequency signal. The filter235 low-pass-filters the frequency signal and outputs the filteredfrequency signal as the oscillation signal of which frequency controlledin accordance with the frequency data “a”.

(Seventh Embodiment)

FIG. 11 is a block diagram of a noninvasive continuous blood pressuremeasuring apparatus of a seventh embodiment of this invention. Thenoninvasive continuous blood pressure measuring apparatus of the seventhembodiment is substantially the same as that of the fourth embodiment.The difference is in the structure of the oscillator. The oscillator 1 dof the seventh embodiment includes a microprocessor (MPU) 241 forreceiving frequency control data, a PLL circuit 247, and a filter 246.The PLL circuit 247 includes a frequency reference signal generatingcircuit 240 for generating a frequency reference signal, a phasecomparator 242 for detecting a phase difference between the frequencyreference signal generating circuit 240 and a frequency-divided signal,an integrator 243 for integrating an output of the phase comparator 242,a voltage-controlled oscillator 245 for generating an oscillation signalof which frequency controlled in accordance with the output of theintegrator, i.e., the integrated phase difference, and a frequencydivider 244 for frequency-dividing the oscillation signal from thevoltage controlled-oscillator 245 by the frequency control data from themicroprocessor 241. The filter 246 removes unnecessary components in theoscillation signal from the voltage controlled oscillator 245 andsupplies the filtered oscillation signal to the exciter 2 and thecalculation portion 7. The frequency of the oscillation signal and thevibration frequency of the exciter 2 are controlled in accordance withthe frequency control data.

(Eighth Embodiment)

FIG. 12 is a block diagram of a noninvasive continuous blood pressuremeasuring apparatus of an eighth embodiment of this invention. Thenoninvasive continuous blood pressure measuring apparatus of the eighthembodiment is substantially the same as that of the fourth embodiment.The difference is that a microprocessor 301 is further provided forfiltering processes and a phase detection process.

The noninvasive continuous blood pressure measuring apparatus of theeighth embodiment includes the oscillator 1 a for generating theoscillation signal 214 a of which frequency controlled to apredetermined (desired) frequency and the corresponding oscillationsignal data 210 a, a bandpass filter 314 for bandpass-filtering theoscillation signal data 210 a and outputting frequency reference signaldata 314 a, the exciter 2 for inducing exciter waveforms in an artery 20and a blood 23 in the artery of a living body (arm) 21, the sensor 3apart from the exciter 2 by a distance D2 for receiving exciterwaveforms and a natural blood pressure waveform from the living body andoutputting detection signal, a pre-amplifier 302 for amplifying thedetection signal including a plurality of patient's physiologicalparameters, an a/d converter 5 for a/d-converting an output of of thepre-amplifier 302 to output detection data, the microprocessor 301 foreffecting a bandpass filtering process for detecting the exciterwaveform and a low pass filtering process for detecting a natural bloodpressure wave form from the detection data and a phase detection processto output phase difference data, a calibration hemadynamometer 6 fordetecting absolute values of a maximum blood pressure and a minimumblood pressure of the living body, a calculating portion 7 forsuccessively calculating and outputting an instantaneous blood pressurevalue from a phase relation between the frequency reference signal dataand the detected exciter waveform and the detected natural bloodpressure waveform and the absolute values from the calibrationhemadynamometer 6, and a display 8 for displaying a continuous bloodpressure variation from the instantaneous blood pressure successivelyoutputted by the calculation portion 7.

The bandpass filtering process portion 304 in the microprocessor 301detects the exciter waveform from the detection data and the low passfiltering process portion 305 detects the natural blood pressurewaveform from the detection data. The phase detection process portion305 detects a phase difference between the frequency reference signaldata 314 a and the detected exciter waveform from the bandpassprocessing portion 304 and outputs the phase difference data including areal number component of the phase shift and an imaginarily numbercomponent of the phase shift.

The calculating portion 7 successively calculates and outputs aninstantaneous blood pressure value from the phase difference data, thedetected natural blood pressure waveform, and the absolute values fromthe calibration hemadynamometer 6. The display 8 displays a continuousblood pressure variation from the instantaneous blood pressuresuccessively outputted by the calculation portion 7.

FIGS. 13A and 13B are graphical drawing of the eighth embodiment. Thesensor receives the vibrations from the living body including theexciter waveform and the natural blood pressure waveform superimposedwith each other. The bandpass filtering processing portion 304 extractsthe exciter waveform 152 and the low pass filter processing portion 305extracts the natural blood pressure waveform 151.

The band pass filter 314 may be omitted if the oscillation signal data210 a includes unnecessary components. The microprocessor 301 may alsoeffect the processing in the calculation portion 7.

(Ninth Embodiment)

FIG. 14 is a block diagram of a noninvasive continuous blood pressuremeasuring apparatus of a ninth embodiment of this invention. Thenoninvasive continuous blood pressure measuring apparatus of the ninthembodiment is substantially the same as that of the ninth embodiment.The difference is that the bandpass filtering process is effected by abandpass filter 404 instead the bandpass filtering processing portion304, the low pass filtering processing is effected by a low pass filter405 instead the low pass filtering processing portion 305, a selector407 is further provided to supplying either of an output of the bandpassfilter 404 and an output of the low pass filter 405 to the a/d converter5.

The sensor 3 receives the induced exciter waveform and natural bloodpressure waveform from the living body and outputting detection signal.The pre-amplifier 302 amplifies the detection signal including aplurality of patient's physiological parameters. The bandpass filter 404extracts the exciter waveform. The low pass filter 405 extracts thenatural blood pressure waveform. The selector switchably outputs eitherof the exciter waveform from the bandpass filter 404 or the naturalblood waveform from the low pass filter 405 in response to a switchingcontrol signal from the microprocessor 301. The a/d converter 5a/d-converts the exciter waveform and the natural blood pressurewaveform. The phase detection process portion 306 detects the phasedifference between the frequency reference signal data 314 a and anoutput of the a/d converter 5 while the selector selects the exciterwaveform and outputs the phase difference data. The calculating portion7 successively calculates and outputs an instantaneous blood pressurevalue from the phase difference data from the phase detection processingportion 306, the natural blood pressure wave form from the a/d converter5 while the selector 407 selects the natural blood pressure wave form,and the absolute values from the calibration hemadynamometer 6. Thedisplay 8 displays a continuous blood pressure variation from theinstantaneous blood pressure successively outputted by the calculationportion 7.

(Tenth Embodiment)

FIG. 15 is a block diagram of a noninvasive continuous blood pressuremeasuring apparatus of a tenth embodiment of this invention. Thenoninvasive continuous blood pressure measuring apparatus of the tenthembodiment is substantially the same as that of the fourth embodiment.The difference is that a reference sensor 501 is further provided withthe exciter 2, an amplifier 504 for amplifying the reference sensordetection signal from the reference sensor 501, and a a/d converter 505for a/d-converting the sensor detection signal from the amplifier 504,and a frequency determining portion 509 are further provided. Thereference sensor 501 detects the vibrations from the exciter 2. Asubstrate 502 supports the exciter 2 and the reference sensor 501.

FIG. 16 depicts a flow chart of the tenth embodiment showing anoperation of the microprocessor 508.

Before detecting the continuous blood pressure, the frequencydetermining portion 509 successively generates and supplies frequencycontrol data indicative of a frequency fi (f1 to fn) to the oscillator 1a for T seconds and successively detects the detection signal from thesensor 3 and the reference sensor detection signal 503 for the intervalof T seconds to determine the optimum frequency and supplies thefrequency control data indicative of the optimum frequency in step S551.When the optimum frequency has been determined, the microprocessor 508successively calculates the instantaneous blood pressure in step S552 atthe optimum frequency, so that the display 8 displays the continuousblood pressure variation from the successively supplied blood pressurefrom the calculation portion 7.

FIG. 17 depicts a flow chart of the tenth embodiment showing anoperation of the frequency determining portion 509, that is, the stepS551.

At first, the frequency determining portion 509 generates the frequencycontrol data indicative of a frequency f1 for the interval of T secondsin step S500. During the interval of T seconds, the oscillator 1 agenerates the oscillation signal having a frequency f1, i.e., A sin(2πf1t). The exciter 2 generates vibration of the frequency f1, so that theexciter waveform is induced in the artery 20.

In the following step S501, the reference sensor 501 detects thevibrations of the exciter 2 and generates the reference sensor detectionsignal 503 which is supplied to the microprocessor 508 through theamplifier 504 and the a/d converter 505 at the oscillation frequency f1.The sensor 3 detects the exciter waveform transmitted through the artery20 and generates the detection signal 3 a which is supplied to themicroprocessor 508 through the amplifier 506 and the a/d converter 507at the oscillation frequency f1. Further, the frequency determiningportion 509 extracts the frequency component f1 from the detectionsignal from the sensor 3 and extracts the frequency component f1 of thereference sensor detection signal by a filtering process.

Moreover, the frequency determining portion 509 effects a quadraturedetection to obtain and store a real number component (I component) andan imaginarily number component (Q component) of the phase shift betweenthe frequency reference signal data and the detection signal from thesensor 3. The processing in step S501 is repeated for T seconds.

FIG. 18 is a graphical drawing of the tenth embodiment.

When t=T (sec) in step S502, the frequency determining portion 509, instep S503, predicts a circular arc 1901 of the I and Q components ((I1,Q1),(I2, Q2), . . . ,(Im, Qm)) of the phase shift at the frequency f1 inan I-Q plane as shown in FIG. 18 and predicts a center 1902 of thecircular arc 1901 and obtains distances, i.e., radiuses, (r1, r2, . . .,rm) between the respective points (I1, Q1),(I2, Q2), . . . ,(Im, Qm)and the predicted center 1902 of the circular arc 1901 (m is a naturalnumber more than one) and calculates an average radius Rf1AVe andattenuation ratio Pf1 with respect to the amplitude Aex of the referencesensor detection signal from the reference sensor 501 as follows:

Pf 1=1·(Rf 1 Ave/Aex)

The frequency determining portion 509, in step S504 calculates adispersion value Rf1Var of the radiuses r1, r2, . . . , rm. Moreover,optimum frequency estimation value Zfi is obtained:

Zf 1=α·(Pf 1 /PStd)+β·(Rf 1 Var/RStd)

Then, processing returns to step S500 to generates the oscillationsignal having a frequency f2.

The processing from steps S500 to S505 is repeated until i=n (n is anatural number).

Then, the optimum frequency estimation values of f1 to fn are obtainedfrom the equation:

Zfi=α·(Pfi/PStd)+β·(RfiVar/RStd)

Then, in step S506, the optimum frequency showing the lowest the optimumfrequency estimation value is selected. In the following step S507, thefrequency determining portion 509 supplies the frequency control data ofthe optimum frequency.

In the equation for obtaining the optimum frequency estimation value, αand β are weighting coefficients which are determined in accordance withdegrees of importance of the estimation element of (Pfi/PStd) and(RfiVar/RStd).

In this embodiment, the reference sensor 501 is used. However, thissensor can be omitted because the amplitude of the vibrations of theexciter 2 is substantially constant over a necessary frequency range.Moreover, it is possible that the amplitudes of the reference sensordetection signal with respect to f1 to fn can be measured and stored inadvance to be used in step S501.

(Eleventh Embodiment)

FIG. 19 is a block diagram of a noninvasive continuous blood pressuremeasuring apparatus of an eleventh embodiment of this invention. Thenoninvasive continuous blood pressure measuring apparatus of theeleventh embodiment is substantially the same as that of the tenthembodiment. The difference is that the waveform determining portion 1602is provided instead the frequency determining portion 509.

FIG. 20 depicts a flow chart of the eleventh embodiment showing anoperation of the microprocessor 1603.

Before detecting the continuous blood pressure, the waveform determiningportion 1602 successively generates and supplies waveform control data1601 indicative of a waveform Wj (j=1 to n) to the oscillator 1 e for Tseconds and successively detects the detection signal from the sensor 3and the reference sensor detection signal 503 for the interval of Tseconds to determine the optimum frequency and supplies the frequencycontrol data indicative of the optimum waveform in step S561. When theoptimum waveform has been determined, the microprocessor 1603successively calculates the instantaneous blood pressure in step S562,so that the display 8 displays the continuous blood pressure variationfrom the successively supplied blood pressure from the calculationportion 7.

FIG. 21 depicts a flow chart of the eleventh embodiment showing anoperation of the waveform determining portion 1602, that is, the stepS561.

At first, the waveform determining portion 1602 generates the waveformcontrol data indicative of a waveform Wj for the interval of T secondsin step S600. During the interval of T seconds, the oscillator 1 egenerates the oscillation signal having a waveform W1, for example Asin(2π ft). The exciter 2 generates vibration of the waveform W1, sothat the exciter waveform is induced in the artery 20.

In the following steps S601 to S605, the waveform estimation value isobtained as similar to the steps S501 to S505. The estimation value isgiven by:

Zwj=α·(Pwj/PStd)+β·(RwjVar/RStd)

Then, processing returns to step S600 to generates the oscillationsignal having a waveform wj.

The processing from steps S600 to S605 is repeated until j=n (n is anatural number).

Then, the waveform estimation values of W1 to Wn are obtained from theequation:

Then, in step S606, the optimum waveform showing the lowest waveformestimation value is selected. In the following step S607, the waveformdetermining portion 1602 supplies the waveform control data of theoptimum waveform.

In this embodiment, the reference sensor 501 is used. However, thissensor can be omitted because the amplitude of the vibrations of theexciter 2 is substantially constant over waveform W1 to Wn. Moreover, itis possible that the amplitudes of the reference sensor detection signalwith respect to waveforms W1 to Wn can be measured and stored in advanceto be used in step S601.

What is claimed is:
 1. A noninvasive continuous blood pressure measuringapparatus comprising: oscillating means for generating an oscillationsignal having a desired frequency and a desired amplitude; a substrate;a plurality of exciters arranged on said substrate in a directionresponsive to said oscillation signal for inducing exciter waveforms inan artery and blood in said artery of a living body; a plurality ofsensors respectively arranged on said substrate in said direction ofpredetermined distance apart from said exciters for receiving inducedexciter waveforms transmitted through said artery from said living bodyand outputting detection signals; switching means for effectingrecurrently switching and time-divisionally outputting outputs of saidsensors; determining and selecting means responsive to said switchingmeans for determining one of said sensor outputs in accordance with anoutput of said switching means and a predetermined judging condition andfor selecting and outputting said one of said sensor outputs;calibration hemadynamometer means for detecting absolute values of amaximum blood pressure and a minimum blood pressure of said living body;calculating means for receiving said absolute values from saidhemadynamometer means and successively calculating and outputting aninstantaneous blood pressure value from a phase relation between saidoscillation signal and said one of said outputs from said determiningand selecting means and said absolute values; displaying means fordisplaying a continuous blood pressure variation from said instantaneousblood pressure successively outputted by said calculation means; whereinsaid substrate correspondingly arranges said exciters and said sensorssuch that pairs, each of which includes an exciter and a sensor, arearranged in said direction and said exciter and said sensor of each pairare arranged in a second direction perpendicular to said direction; andattaching means for attaching said substrate to said living body.
 2. Anoninvasive continuous blood pressure measuring apparatus comprising:oscillating means for generating an oscillation signal having a desiredfrequency and a desired amplitude; a substrate; a plurality of excitersarranged on said substrate in a direction responsive to said oscillationsignal for inducing exciter waveforms in an artery and blood in saidartery of a living body; a plurality of sensors respectively arranged onsaid substrate in said direction of predetermined distance apart fromsaid exciters for receiving induced exciter waveforms transmittedthrough said artery from said living body and outputting detectionsignals; switching means for effecting recurrently switching andtime-divisionally outputting outputs of said sensors; determining andselecting means responsive to said switching means for determining oneof said sensor outputs in accordance with an output of said switchingmeans and a predetermined judging condition and for selecting andoutputting said one of said sensor outputs; calibration hemadynamometermeans for detecting absolute values of a maximum blood pressure and aminimum blood pressure of said living body; calculating means forreceiving said absolute values from said hemadynamometer means andsuccessively calculating and outputting an instantaneous blood pressurevalue from a phase relation between said oscillation signal and said oneof said outputs from said determining and selecting means and saidabsolute values; displaying means for displaying a continuous bloodpressure variation from said instantaneous blood pressure successivelyoutputted by said calculation means; wherein said substratecorrespondingly arranging said exciters and said sensors such thatgroups include two of said sensors and one of said exciters, the exciterof each group arranged between two of said sensors of the group withsaid predetermined distance between an exciter and the two sensors ofeach group, the groups being arranged along said direction; andattaching means for attaching said substrate to said living body.
 3. Thenoninvasive continuous blood pressure measuring apparatus as claimed inclaim 1, further comprising: a plurality of a/d converters forrespectively a/d-converting said detection signals and supplyingconverted signals to said determining and selecting means as saidoutputs of said sensors.
 4. The noninvasive continuous blood pressuremeasuring apparatus as claimed in claim 2, further comprising: aplurality of a/d converters for respectively a/d-converting saiddetection signals and supplying converted signals to said determiningand selecting means as said